Method of making hollow metallic articles



*July 9. 1929.I F. c. LANGENBERG 1.720.366

METHOD OF MAKING HOLLOW METALLIC ARTICLES Filed Dec. ll, 1925 PatentedJuly 9, 1929.

UNITED STATES PATENT OFFICE.

FREDERICK C. LANGENBERG, OF WATERTOWN, MASSACHUSETTS, ASSIGNR Oli' ONE-I-IALF T0 TRACY C. DICKSON, OF WATERTOVN, MASSACHUSETTS.

METHOD OF MAKING HOLLOW METALLIC ARTICLES.

Application filed December 11, 1925. Serial No. 74,816.

My present invention relates to a novel method of manufacturing hollowmetallic articles and particularly those made of steel. In my priorPatent No. 1,553,824, September 15, 1925, I have described a method formak ing metallic articles which consists essential ly in expanding thearticle to a point beyond the elastic limit of the material employedwhile it is contained within a jacket which stops the expansion when apredetermined point has been reached. In another prior Patent No.1,552,848, Se} 3tember 8, 1925, I have described another method whichincludes annealing the material after the first expansion and then againexpanding it to a point beyond its elastic limit. As explained in thispatent, the strength of the article produced is increased by interposingthe annealing step between the expanding' steps.

I have discovered that when a unitary cylinder is expanded beyond theelastic limit of the metal composing it, the elastic limit of the. metalat the bore will` be raised to a greater extent than that of the metalat the outside of the cylinder. Consequently the total elastic strengthof the article, that is, the total ability of the article to resist an:internal pressure without permanent distor t-ion is not as great as itwould be if the elastic limit of the met-al in the outer parts of thestructure had been distributed in a different manner.

My improved process makes it possible to produce a hollow colchworkedarticle, the elastic limit to whose exterior layer of metal is notgreatly different from that of its interior layers, so that the totalstrength of an article of a given weight and material is much increased.

The hereindescribed novel method therefore produces composite articleswhich are stronger for a given weight and material, or are lighter for agiven strength than articles made of a single piece of metal asdescribed in my said prior patents.

The hereindescribed novel method is particularly applicable to lthemanufacture of large guns and similar articles and does away with theexpensive, diflicult and unreliable methods of shrinking on successiverings which have heretofore been commonly employed in the manufacture ofguns. The compound guns manufactured by the hereindescribed improvedmethod have an elastic strength materially greater than either aone-piece gun made by the methods described 1n my two prior patentsabove mentioned, or of a built-up gun made by the ordinary method ofshrinking on rings.

In the 'followingAdcscrii'ition, I have explaiiied the method of makinga cylinder havmg two concentric rings, the outer of which has beenexpanded more than the inner and consequently has a greater elasticstrength. rThe hercindescribed method is however applicable to theproduction of articles having more thanv two rings, and to those inwhich the ring having the highest elastic limit is placed in any desiredkposition with relation to the other rings composing the finishedarticle. I believemy invention to be a broad one and therefore do notintend any limitations not expressly contained 'in the claim forming apart thereof.

The :invention will be fully understood from the following descriptionwhen taken in connection with the accompanying drawings, and the .novelfeatures thereof will be pointed out and clearly defined in the claim atthe close of this specification.

In the (ilrawings:

Fig. 1 shows the in process of being Fig. 2 shows the being annealed.

Fig. 8 shows the outer concentric member being assembled with anunexpandcd inner member.

Fig. lshows the two members being oxpanded. I

F 5 shows the annealing of the two members.

Fig. 6 shows the two members being again expanded.

Figs. 7 and 8 are diagrams illustrating the effects of thehereindescribed process.

Referring now to the drawings:

At A is shown, what for convenience may be termed the outer concentricmember, which is of steel or a suitable alloy. In practicing mypreferred method, this member is expanded by the aplnu'atus described inmy prior Patent No. ',553,824l, lthe expansion being' carried to a pointbeyond the elastic limit of the material and thereby increasing :itselastic strength. The piece is preferably then annealed as described inmy prior Patent No. 1,552,848, this being shown in Fie". 2. Next,concentric inner outer concentric member exl'ianded. outer concentricmember llt) member B of an exterior diameter such that it will fitclosely Within the bore of member A is assembled With it. (See Fig. Thetwo then aresimiiltaneously expanded (see Fig. 4t) as previouslydescribed, thereby raising the elastic limit ot both members A and B.Thereafter (see Fig. the Whole is annealed and is again expanded. (SeeFig. G.) It Will be understood that the expanding and annealingsteps maybe continued according to the linal results desired.

The article in the condition shown may then be finished; if itis'intended tor use as a gun, it Will be ritied.

The effects oit the procedure already described ivill be best understoodfrom an examination and comparison oi" tlie diagrams contained inV Figs.7 and 8. In Fig. 7 is shown a tube M having,r a thickness ol? onecalibre. If it be assumed that this tube has been expanded in accordancewith the method kdescribed in my prior Patent No. 1,553,824-, andtest-bars are cut from the meta-l to determine the elastic limit et themetal at different points along the radial line t o, it will be foundthat the elastic limit diminishes toward the exterior, as shown by thecurve (l d, which shows the elastic limits plotted against the distancesradially. This decrease iii elastic limit is due to the fact that theamount et increase in elastic limit'resulting` from cold working' suchvas takes place when the tube is expanded is a function of the amount offlow of the metal, and since the metal on the outside ot' the tube flowslesslthan that at the center, the increase in elastic limit is less. Itresults that the capacity otl the metal on the outside of the tube toWithstand expansion is not being used to the fullest possible extent.

In Fig. 8, I have shown a tube made up of two concentric members N andO, both of which have been expanded as previously explained. In thiscase the outer member Was expalnded separately and the elastic limit oithe material raised, as Ishown by the curve g 1' in dotted lines. Theiimer member was then inserted and the two members simultaneouslyexpanded. The curve e f indicates the elastic limit ol' the inner memberWhile the curve yf/ i, indicates that of the outer member al'ter thetinal expansion. It will theretore be seen that the elastic strength otthe outer member is considerably greater tlan that oll thecorrespondiimy Zone of the unitary tube shown in Fig. 7, and that of thelinished tube as a whole is correspondiugly greater. In other words, theelastic strengths oilE the outer layer ol the outer member and o't theinner layer of the inner member are not materially dillerent and theformer is equal to or greater than the latter.

As a consequence olf these, facts, the elastic limit of each section,except the inner one, is greater than the elastic limit ot theeorrespondingr saone ot a unitary cylinder ot identical size andcomposition, and the elastic strength et the composite tubeI as a wholeis greater than that ot a. unitary tube o'l like size and compositiondue not only to increased elastic limit of the outer metal, butincreased compression of metal at the bore. 'It will be understood, o ifcourse, that these ligiii'es are merely diagrams to maliey the ellectmore clear, and make no attempt, to represent t-lie conditionsaccurately.

IVhat I claim is:

rllhe method of makingr hollow articles Which comprises expanding;` a`hollow tubu* lar member to increase its elastic limit, assemblingtherewithin a. second tubular member and subjecting' the latter toexpansion until the elastic limit ot its inner layer is not materiallydifferent 'from that ot the, oiitei' layer of the lirst mentionedmember.

In testimony whereof I allix my signa ture.

FREDERICK C. LANGENBIIRG.

